FXUS65 KPSR 232129
AFDPSR

AREA FORECAST DISCUSSION 
NATIONAL WEATHER SERVICE PHOENIX AZ
230 PM MST WED DEC 23 2009

.SYNOPSIS...
A HIGH PRESSURE SYSTEM WILL SLOWLY BUILD INTO THE REGION FOR SUNNY 
SKIES THURSDAY AND CHRISTMAS DAY. DRY WEATHER WILL CONTINUE THIS 
WEEKEND...BUT WITH VARIABLE HIGH CLOUDS. ANOTHER PACIFIC COLD FRONT 
IS EXPECTED TO MOVE INTO THE AREA MONDAY...WITH INCREASING CLOUDS 
AND A SLIGHT CHANCE OF SHOWERS FOR MOST AREAS. 

&&

.DISCUSSION...
THE STRONG COLD LOW PRESSURE SYSTEM THAT MOVED INTO ARIZONA TUESDAY 
AND TUESDAY NIGHT HAS NOW MOVED INTO NEW MEXICO. DRY NORTHWEST FLOW 
ALOFT WILL FOLLOW TONIGHT THROUGH FRIDAY NIGHT FOR MOSTLY CLEAR 
SKIES AND BELOW NORMAL TEMPERATURES.

THIS WEEKEND...
DRY WEATHER. INCREASING WESTERLY FLOW ALOFT WILL RESULT IN SLIGHTLY 
WARMER TEMPERATURES...AND VARIABLE HIGH CLOUDS. HIGH CLOUDS WILL BE 
IN ADVANCE OF ANOTHER PACIFIC COLD FRONT EXPECTED SOMETIME MONDAY.

MONDAY AND TUESDAY...
THE NEXT PACIFIC WEATHER SYSTEM FOR MONDAY IS CURRENTLY IN THE 
WESTERN PACIFIC...AND BEING PUSHED ALONG BY 185 MPH JET STREAM 
WINDS. THIS SYSTEM WILL UNDOUBTEDLY GO THROUGH EVOLUTIONARY CHANGES 
BEFORE ARRIVING IN ARIZONA EARLY NEXT WEEK. AT THIS POINT...MEDIUM 
RANGE MODELS SHOW TIMING AND INTENSITY DIFFERENCES WITH THIS NEXT 
SYSTEM...BUT NONETHELESS STILL PROJECT A WEATHER CHANGE FOR EARLY 
NEXT WEEK.  

BOTH EUROPEAN AND GFS MODELED SOUNDINGS FOR AZ MONDAY/MONDAY NIGHT 
SHOW ATMOSPHERIC SATURATION TO THE POINT OF POSSIBLE SHOWER 
ACTIVITY.  THEREFORE...WE WILL INTRODUCE A SLIGHT CHANCE OF SHOWERS 
AREA-WIDE MONDAY AND TUESDAY TO REFLECT THE EXPECTED CHANGE. 
FORECASTS WILL BE FINED TUNED IN THE COMING DAYS AS THE WEATHER 
SYSTEM TRANSITIONS THROUGH THE EASTERN PACIFIC AND CLOSER TO THE 
WEST COAST. 

 
&&

.AVIATION...
THE MID-LEVEL CENTER OF CIRCULATION...CURRENTLY POSITIONED OVER 
CENTRAL NEW MEXICO...WILL CONTINUE ITS EASTWARD MIGRATION. THUS THE 
CLEARING TREND WILL CONTINUE THROUGH TODAY FROM WEST TO EAST AS HIGH 
PRESSURE SLOWLY BUILDS OVER THE REGION. SKIES ARE ALREADY CLEAR OVER 
THE WESTERN TAF SITES...KIPL/KBLH...WITH CLEARING OVER KPHX/KIWA 
ANTICIPATED BY LATE THIS AFTERNOON. WINDS COULD BE GUSTY OUT OF THE 
NORTHWEST TODAY AT ALL SITES...ESPECIALLY KBLH...BUT NOT AS STRONG 
AS YESTERDAY. WINDS WILL BECOME LIGHT AND CONFORM TO MORE TYPICAL 
DIURNAL PATTERNS GENERALLY AFTER 06Z THURSDAY.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS. 

&&

.FIRE WEATHER...
FRIDAY THROUGH TUESDAY...
MUCH LOWER HUMIDITY SPREADING ACROSS THE REGION FROM THE NORTH. 
OTHERWISE DRY WEATHER WITH BELOW NORMAL TEMPERATURES THROUGH THE 
WEEKEND. RH WILL INCREASE EARLY NEXT WEEK AS LOW PRESSURE APPROACHES 
THE REGION FROM THE WEST.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

NATIONAL WEATHER SERVICE PHOENIX IS ON THE INTERNET AT

WEATHER.GOV/PHOENIX

DISCUSSION...VASQUEZ 
AVIATION...PADDOCK
FIRE WEATHER...LEINS